The invention relates to an ink jet printer with a covering and cleaning device for the ink nozzles of an ink jet print head, which covering and cleaning device are mounted on a segment of a periphery of a disk, which is arranged in the area of the ink jet printer and which rotates on an axis extending through a circle.
An ink jet printer with a covering and cleaning device for the ink nozzles of an ink jet print head is disclosed by DE-C-36 11 666. Described in this document is an ink jet print head which can be displayed parallel to a print line and a roll-like print backing support used to support a recording medium opposite the ink jet print head and aligned parallel to the print line. Arranged alongside the printing area, that is to say the maximum area which can be assumed by the recording medium and the maximum area which can be printed by the ink jet print head, is a parking area having a covering device and a cleaning device for the ink nozzles of the ink jet print head.
As a result of the parking area, the printer obtains a width which cannot be accepted in many applications. This applies in particular to cashdesk printers of the type as described, for example, in the German patent application 197 09 941.6. Such cashdesk printers are often installed in a cutout in a cashdesk, so that for their outline a quasi-standard has been formed, having a width dimension which is only slightly greater than the width of the largest document to be printed with the printer. This document is in DIN A4 format, that is to say has a width of 210 mm. In printers of this class, the ink jet printing principle has therefore not been used hitherto.
It has already been proposed, in U.S. Pat. No. 5,051,761, to fit the covering device and the cleaning device on the periphery of a circular or circular-segment-like disk arranged in the printing area of the ink jet print head, and it is possible for the disk to rotate about an axis extending through the center of the circle. In this case, the recording medium is supported in the printing area by an endless transport belt, which is stretched out between two deflection rollers. One of these transport rollersxe2x80x94as viewed in the transport direction of the recording mediumxe2x80x94is arranged upstream of the printing area and the other is arranged downstream of the latter. Cut out of the transport belt is a window, through which the covering device or the cleaning device act on the ink jet print head if the disk is lifted in the direction of the printing area. The arrangement comprising transport belt and deflection rollers is complicated and needs a relatively great amount of space. Added to this is the fact that the transport belt firstly has to be brought into a specific peripheral position relative to the ink jet print head before the covering device or the cleaning device can act on the ink jet print head. This requires additional monitoring devices and control measures for positioning the transport belt, and makes the printer slower, since the recording medium must have left the transport belt before the window can be brought into the area of the ink jet print head.
The object of the invention is to provide an ink jet printer having a covering and cleaning device arranged in the printing area of the ink jet print head for the ink nozzles of the ink jet print head, and to propose a supporting device, for a recording medium, which can be brought into the printing area instead of the covering and cleaning device.
The object is achieved by an improvement which is that a disk with the covering device and the cleaning device in position in a gap between two parts of a print backing support, and has a supporting section for the recording medium arranged on a segment of the periphery which can be rotated into position during printing.
The covering device and the cleaning device are arranged in the printing area of the ink jet print head. The fact that the covering device, the cleaning device and the supporting section for the recording medium are arranged on the periphery of a circular or circular-segment-like disk which can be rotated about an axis extending through the center of the circle, means that no additional space is needed for a parking area outside the printing area or upstream and downstream of the ink jet print head. The disk can be arranged in the printing area anywhere within the print line. As a result of the rotation of the disk about its axis, the covering device can be brought in front of the nozzle plate of the ink jet print head, the cleaning device can be moved past the nozzle plate, or the supporting section can be pivoted into the printing area. Since the covering device must in any case be pivoted away in front of the nozzle plate before a printing operation, the supporting section can be brought into the printing area without additional effort by simply rotating the disk further.
The axis can be aligned either parallel to the print backing support or perpendicular thereto and parallel to the plane of the recording medium.
The disk is preferably rotated by a motor, in particular a stepping motor. In the latter case, the angular position of the disk can be fixed simply by counting the motor stepping pulses. The drive to the disk is preferably provided via a toothing system, at least on part of its periphery, which meshes with a gear wheel driven by the motor.
In a preferred development of the invention, the disk can be displaced along the print backing support. As a result, in the case of a cashdesk printer having a receipt printing station, such as is disclosed by the German patent application 197 09 941.6, the disk can be displaced into the part of the printing area which is not occupied by the receipt paper strip. If a receipt printing station and a journal printing station are used alongside each other, the disk can be brought into the gap between the receipt paper strip and the journal paper strip.
In order to ensure that the covering device is lifted perpendicularly off the nozzle plate of the ink jet print head, the covering device is connected to the disk via a radially adjustable slider, and fixed to the slider is a control pin which is guided in a snail-shaped or spiral control curve arranged in the ink jet printer and surrounding the axis. The control curve is formed on a control plate which is held on the axis and is stationary with respect to the disk, that is to say does not rotate together with the disk.
Further features and advantages of the invention emerge from the following description which, in conjunction with the appended drawings, explain the invention using exemplary embodiments.